Method for continuous refining of fatty oils



Jan. 3, 1956 1. A. AFZELIUS 2,729,662

METHOD FOR CONTINUOUS REFINING OF FATTY OILS Filed June 10, 1952 INVENTOR. jvar sgxel flfzelz'ua' United. States Patent 2,729,662 METHOD FOR CONTINUOUS REFINING BF FATTY OILS Ivar Axel Afzelius, Bromma, Sweden, assignor to Aktiebolaget Separator, Stockholm, Sweden, a corporation of Sweden Application June 10, 1952, Serial No. 292,650 Claims priority, application Sweden June 26, 1951 3 Claims. (Cl. 260-425) This invention relates to an improved method of refining fatty oils in a continuous operation with the use of alkali as a refining agent.

It is known to neutralize fatty oils in a continuous operation with alkali, e. g. soda lye and soda. It is likewise known to treat the neutralized oil subsequently with alkali, such as soda lye, soda and sodium silicate or mixtures thereof, considerable improvements of the color, flavor and odor of the refined oil being thereby obtained. See, for example, U. S. Patent No. 1,169,155. It is known, too, that the quality of a fatty oil can be improved by deodorization, that is, by blowing steam into it in a vacuum, whereby certain volatile substances are eliminated.

I have discovered that a considerable improvement of the quality of the refined oil can be obtained if the oil, in a continuous operation, is first neutralized with alkali, then subjected to a separating operation to remove the soap thus formed, and subsequently treated with alkali while blowing steam into the oil, thereby producing an intimate mixing of the reaction mixture and thus ameliorating considerably the reaction between oil and alkali and, consequently, the refining result. After removal of the soap formed again, the oil can finally be deodorized in the known way by steam blowing as mentioned above.

The method can be used to particular advantage when refining certain oils which are difficult to refine, such as rape oil, soya-bean oil or fish oil, which often have a characteristic flavor and when stored for a long period after the refining will again acquire their characteristic flavor.

The method is described more in detail below, reference being made to the accompanying drawing, in which the single illustration is a schematic view of a preferred system for use in carrying out the process.

The oil to be refined is led through a pipe 1 into a mixer 2 where it is neutralized by lye introduced through a pipe 3. The oil is then led through a pipe 4 into a hermetically closed centrifugal. separator 5 where the soap formed is separated out and discharged through a pipe 6. The oil thus neutralized and centrifuged is led through a pipe 7 to a mixer 8. By introducing steam into the oil through a pipe 9, the oil is heated to a temperature of'approximately 100 C., for instance 98 C. in the mixer 8, lye is added to the oil through a pipe 10. From'the mixer 8 the oil passes through a pipe 11 into a reaction vessel 12, through which steam is blown. The steam is introduced into the vessel 12 (and the oil therein) through a pipe 13, the excess steam escaping at atmospheric pressure at the top of the vessel 12 through a pipe 14. Since the oil has been heated to about 100 C. before the second alkali-treatment step, the formation of condensate is avoided in the vessel 12. While there will thus be no dilution of the lye, practically all of the steam supplied to the vessel 12 flows through the latter and leaves through the pipe 14, thereby producing an intimate mixing of oil and lye and, consequently, a considerably amel iorated reaction. From the vessel 12, the oil leaves via an overflow discharge through a pipe 15 to an open-type centrifugal separator 16, where the newly-formed soap is separated out and discharged through a pipe 17. The separated oil is discharged through a pipe 18, to be subsequently washed, dried, bleached and deodorized in the known way. For the second stage of the alkali treat- Patented Jan. 3, 1956 meat, soda lye or potash lye, soda, water glass, etc., or mixtures thereof, can be used.

The efiect of the method according to the present invention will be seen from the following examples, of which the Examples 1 and 2 are representative of the practice prior to the present invention, whereas the Example 3 is representative of the present invention.

Example1.--A rape oil with a free fatty acid content of 2% was neutralized by admixing the necessary quantity of 15% soda lye. After centrifugally separating the soap thus formed, the oil was washed with water, dried under vacuum, bleached with 1% bleaching earth and deodorized by blowing steam of 180 C. into it for four hours under vacuum. The oil thus refined in the known way had a strong rape-seed taste and received in the fiavor test the figure 3.

When determining the suitableness of the oil for margarine production, the following figures were used: Figure 6 super-fine quality oil, absolutely free from odor and taste. Figure 5 best-quality oil, practically free from odor and taste. Figure 4 good-quality oil, slight rape taste. Figure 3 bad oil, distinct rape taste and distinct rape odor. Figure 2 oil unsuitable for use, strong taste and odor. Figure 1 oil quite unfit for use.

The color (according to Lovibond) of the refined oil was 35 yellow x 5 red.

Example 2.-The same rape oil was neutralized in the manner described above, and the oil was then heated to C. and mixed with 5% of an alkali-solution, consisting of equal parts of 15% soda lye and of 20% soda solution. The mixture was then led to a reaction vessel where it was allowed to repose, without stirring, for 20 minutes. After washing, drying, bleaching and deodorization, which operations were carried out in exactly the same manner as in the previous example, the oil got the flavor-test figure 3+ and its color was 35 yellow x 3.5 red. This improvement is due to the second alkalitreatment stage.

Example '3.-Rape oil was treated in the same way as in Example 2, with the difference, however, that free steam was blown into the reaction vessel while the test was going on. The oil subsequently washed, dried, bleached and deodorized in the aforementioned way, got the taste figure 4+ and had color 35 yellow x 1.5 red. The improvement in this case is due to the blowing of steam into the reaction vessel, as previously described in connection with the vessel 12 of the drawing.

I claim:

1. In the continuous refining of fatty oils by treating the oil with an alkali refining agent in two stages of alkali treatment and in each stage separating the oil from the resulting soap, the improvement which comprises blowing steam through the oil from the first stage separation during the second alkali-treatment stage.

2. The improvement according to claim 1, comprising also the step of heating the oil to about 100 C. prior to said blowing with steam.

3. The improvement according to claim 1, comprising also subjecting the oil from the second alkali-treatment stage to washing, drying, bleaching and deodorization by blowing with steam under vacuum.

References Cited in the file of this patent UNITED STATES PATENTS 653,041 Schlinck July 3, 1900 1,169,155 Holbrook Ian. 25, 1916 1,885,281 Newton Nov. 1, 1932 2,236,493 Moore Mar. 25, 1941 2,268,567 Clayton Jan. 6, 1942 OTHER REFERENCES Schwitzer: Continuous Processing of Fats, 1952, pages 137. and 148 to 159. 

1. IN THE CONTINUOUS REFINING OF FATTY OILS BY TREATING THE OIL WITH AN ALKALI REFINING AGENT IN TWO STAGES OF ALKALI TREATMENT AND IN EACH STAGE SEPARATING THE OIL FROM THE RESULTING SOAP, THE IMPROVEMENT WHICH COMPRISES BLOWING STEAM THROUGH THE OIL FROM THE FIRST STAGE SEPARATION DURING THE SECOND ALKALI-TREATMENT STAGE. 